Today, automation systems are being installed in more and more buildings, including both new construction and in structures that are being rebuilt. The incentives for putting automation systems into a building are numerous. High on the list are reduced operating costs, more efficient use of energy, simplified control of building systems, ease of maintenance and of effecting changes to the systems. Facility managers would prefer to install systems that can interoperate amongst each other. Interoperability is defined by different products, devices and systems for different tasks and developed by different manufacturers that can be linked together to form flexible, functional control networks.
An example of a typical automation system includes lighting controls, HVAC systems, security systems, fire alarm systems and motor drives all possibly provided by different manufacturers. It is desirable if these separate disparate systems can communicate and operate with each other.
Prior art automation systems generally comprised closed proprietary equipment supplied by a single manufacturer. With this type of proprietary system, the installation, servicing and future modifications of the component devices in the system were restricted to a single manufacturer's product offering and technical capability. In addition, it was very difficult or impossible to integrate new technology developed by other manufacturers. If technology from other manufactures could be integrated, it was usually too costly to consider.
An integral part of any automation control system are the sensors and transducers used to gather data on one or more physical parameters such as temperature and motion. One or more sensor functions may be placed in a device and be able to communicate with one or more control units, i.e., processing nodes, on the control network.
In many situations, it is desirable to control the amount of light provided in a given area. Large areas require many individual light sources to provide light coverage for the entire area. Typically, the light sources are either all controlled together or are grouped together into large groups where each group can be controlled. This method of controlling the light sources does not permit fine-tuning of the light level of individual areas within the larger area to be illuminated.
The level of light may be controlled by a light sensor that measures light in units of lux. Typically, the readings from the lux sensor ultimately control the level of light in an area. The disadvantage, however, of this is that in large areas, the reading from the lux sensor would realize a light level in one area of the room without taking into account other areas of the same room. This causes the light level to be either dimmed or too bright in one or more areas.